Classification of Bones

Classification of BonesBones are identified by:

1. ShapeA. Long bonesB. Short bonesC. Flat bonesD. Irregular bones

2. Internal tissuesA. Compact -Strong able to bear

weightB. Spongy – Light, less dense

3. Bone markings

Internal Tissues

Spongy Bone

Compact Bone

Long Bones

• Are typically longer then they are wide

• All of the limbs, except the wrist and ankle bones.

• Mostly compact

Flat Bones• Are thin, flattened and

usually curved

• Found in the skull, sternum, ribs, and scapula

• Have two thin layers of compact bone sandwiching a layer of spongy bone between them

Flat Bones

• The parietal bone of the skullFigure 6–2b

Sutural Bones• Are small, irregular bones• Are found between the flat bones of the skull

Irregular Bones • Have complex shapes • Do not fit one of the other categories• Examples:

Vertebrae Pelvis

Short Bones• Are small and thick• Cube-shaped and contain mostly spongy bone• Examples:

Carpals

Tarsals

Sesamoid (ses’ah-moyd) Bones

Special type of short bone

- Form within tendons- Best known example is the patella

- Develop inside tendons near joints of knees, hands, and feet

The Axial Skeleton

Eighty bones segregated intothree regions

1. Skull2. Vertebral column3. Bony thorax

Vertebral Column

Formed from 26 irregular bones (vertebrae)

Cervical vertebrae7 bones of the neck

Thoracic vertebrae 12 bones of the torso

Figure 7.13

Vertebral Column

Lumbar vertebrae 5 bones of the lower back

Sacrum bone inferior to the lumbar vertebrae that articulates with the hip bones

Figure 7.13

Cervical Vertebrae: The Atlas (C1)

The atlas – Has no body and no spinous process

Cervical Vertebrae: The Axis (C2)

• The axis has a body, spine, and vertebral arches as do other cervical vertebrae

Figure 7.16c

Sacrum and Coccyx

• The sacrum– Consists of five fused vertebrae (S1-S5), which shape

the posterior wall of the pelvis

• Coccyx (Tailbone)– The coccyx is made up of four (in some cases three

to five) fused vertebrae that articulate superiorly with the sacrum

Sacrum and Coccyx

Figure 7.18a

Bony Thorax (Thoracic Cage)Bony Thorax (Thoracic Cage)• The thoracic cage is composed of the thoracic vertebrae, ribs

and the sternum

• Functions– Forms a protective cage around the heart, lungs,

and great blood vessels– Supports the shoulder girdles and upper limbs– Provides attachment for many neck, back, chest,

and shoulder muscles

Bony Thorax (Thoracic Cage)

Figure 7.19a

Sternum (Breastbone)

• A dagger-shaped, flat bone that lies in the anterior midline of the thorax

Ribs• There are twelve pair of ribs forming the flaring sides

of the thoracic cage

• All ribs attach posteriorly to the thoracic vertebrae

• The superior 7 pair (true ribs) attach directly to the sternum via costal cartilages

• Ribs 8-10 (false ribs) attach indirectly to the sternum via costal cartilage

• Ribs 11-12 (floatingribs) have no anterior attachment

Ribs

Figure 7.19a

Appendicular Skeleton

• The appendicular skeleton is made up of the bones of the limbs and their girdles

• Pectoral girdles attach the upper limbs to the body trunk

• Pelvic girdle secures the lower limbs

Pectoral Girdles (Shoulder Girdles)

• The pectoral girdles consist of the anterior clavicles and the posterior scapulae

• They attach the upper limbs to the axial skeleton in a manner that allows for maximum movement

• They provide attachment points for muscles that move the upper limbs

Clavicles (Collarbones)

They provide:

1. attachment points for numerous muscles

2. act as braces to hold the scapulae and arms out laterally away from the body

The Upper Limb

• The upper limb consists of the arm, forearm and hand.

• Thirty-seven bones form the skeletal framework of each upper limb.

Arm

• The humerus is the sole bone of the arm

• It articulates with the scapula at the shoulder, and the radius and ulna at the elbow

Forearm

The bones of the forearm are the 1. Radius2. Ulna

• The ulna lies medially in the forearm and is slightly longer than the radius

• Forms the major portion of the elbow joint with the humerus

Ulna

Hand

• The wrist contains 8 bones

• The palm contains 5 bones

• Each hand contains 14 miniature long bones called phalanges.

Pelvic Girdle (Hip)

Figure 7.27a

Transmits weight of the upper body to the lower limbs

The hip is formed by a pair of hip bones and together with the sacrum and the coccyx, these bones form the bony pelvis

Femur

• The sole bone of the thigh

• Largest and strongest bone in the body

Figure 7.28b

Tibia• Receives the weight of

the body from the femur and transmits it to the foot

FibulaSticklike bone that does not bear weight

Calcaneus

• Forms the heel of the foot

• Point of attachment for the calcaneal (Achilles) tendon of the calf muscles